Dollhouse

Buffy the Vampire Slayer (Riff Regan vs. Alyson Hannigan)

What they changed: Joss Whedon financed the original pilot himself, formatting it as a half-hour episode. It is, for the most part, a shortened version of "Welcome to the Hellmouth," but with different casting. The role of the Sunnydale library was played by Torrance High School’s library — a much larger and airier room than the cramped Hellmouth library we’ve come to know and love, with a handy second floor for showing off those Buffy backflips. Instead of Ken "Hyena Chow" Lerner as Principal Flutie, we get a much more straightlaced interpretation from character actor Stephen Tobolowsky. But perhaps the biggest difference is in the role of Willow. Instead of Alyson Hannigan, the geeky witch was originally played by Riff Regan.

How might the series have been different? Flutie probably would have still ended up in the stomachs of his students, but the Scooby Gang might have never been the same. Regan’s Willow was a sweet doormat, but she didn’t have quite the neurotic, eager-to-please quality Hannigan brought to the role. Incidentally, it wasn’t the first time Hannigan replaced an actress after the filming of a show’s initial pilot. In 1989, she took over the role of Jessie Harper in the fantasy sitcom Free Spirit.